1. Field of the Invention
The present invention relates to a high-purity iron oxide as a raw material of ferrites which is produced from iron ore, and to a method for producing the same.
2. Description of the Prior Art
There are several methods for producing from iron ore an iron oxide as a raw material of ferrites. A common method consists of crushing, classification, and mineral dressing, with the starting material being hematite or magnetite. The mineral dressing includes table gravity concentration, flotation, and magnetic separation. These methods are combined with one another or followed by chemical treatments. The combination of mineral dressing methods is disclosed in Japanese Patent Publication No. 4536/1990 and Japanese Patent Laid-open No. 11526/1988. The chemical treatments following mineral dressing are disclosed in Japanese Patent Laid-open Nos. 295239/1986 and 69527/1989.
The iron oxide produced as mentioned above is mixed with strontium carbonate and barium carbonate in the production of ferrites. The mixing of a plurality of raw materials is accomplished by dry process or wet process, the former consisting of mixing raw materials in dry powder form for several hours in a vibrating rod mill or Eirich mixer, and the latter consisting of mixing raw materials in slurry form (about 50% concentration) for several hours in a mixing ball mill.
There are two kinds of iron oxides as a raw material of ferrites. One is produced by pulverizing iron ore as mentioned above, and the other is produced from iron compounds such as iron chloride and iron sulfate. The former is inferior to the latter; that is, it contains a large amount of impurities such as SiO.sub.2 and Al.sub.2 O.sub.3, which make it unsuitable as a raw material of high-quality ferrites. To address this problem, the present inventors carried out extensive studies and, as the result, succeeded in producing from iron ore a high-purity iron oxide containing less than 0.15% SiO.sub.2 and less than 0.1% Al.sub.2 O.sub.3.
It is an object of the present invention to provide a high-purity iron oxide as a raw material of high-quality ferrites.
It is another object of the present invention to provide a method for producing said high-purity iron oxide from iron ore.
It is another object of the present invention to provide a method for producing a high-purity iron oxide fine powder having a uniform particle size which is suitable as a raw material of high-performance ferrites.